U.S. patent number 7,852,027 [Application Number 11/755,299] was granted by the patent office on 2010-12-14 for method and circuit for testing motor.
This patent grant is currently assigned to Delta Electronics, Inc.. Invention is credited to Shih-Ming Huang, Wen-Shi Huang, Wan-Bing Jin, Li-Jian Wu, Jian-Ping Yang.
United States Patent |
7,852,027 |
Wu , et al. |
December 14, 2010 |
**Please see images for:
( Certificate of Correction ) ** |
Method and circuit for testing motor
Abstract
A method for testing a motor having a rotor and a winding is
provided. The method includes steps of (a) providing a power to
rotate the rotor to a predetermined speed, (b) removing the power,
(c) measuring a terminal voltage of the winding while a current
within the winding is zero, (d) obtaining a back electromotive
force in the winding by compensating the terminal voltage with a
performance of the rotor, (e) selecting a characteristic of the
back electromotive force and (f) determining a magnetization of the
motor by comparing the characteristic with a predetermined
parameter.
Inventors: |
Wu; Li-Jian (Shanghai,
CN), Jin; Wan-Bing (Shanghai, CN), Yang;
Jian-Ping (Shanghai, CN), Huang; Shih-Ming
(Taoyuan Shien, TW), Huang; Wen-Shi (Taoyuan Shien,
TW) |
Assignee: |
Delta Electronics, Inc.
(Taoyuan Hsien, TW)
|
Family
ID: |
38970809 |
Appl.
No.: |
11/755,299 |
Filed: |
May 30, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080018285 A1 |
Jan 24, 2008 |
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Foreign Application Priority Data
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Jun 23, 2006 [TW] |
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95122839 A |
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Current U.S.
Class: |
318/400.34;
318/490; 318/805; 318/459; 318/368 |
Current CPC
Class: |
H02P
23/14 (20130101) |
Current International
Class: |
H02P
6/18 (20060101) |
Field of
Search: |
;318/101,135,400.01,400.06,400.3,400.31,400.32,400.33,400.42,490,799,628,632,638,400.34,159,805,368,432,437,459
;73/609,865.3,865.9 ;388/928.1 ;327/200,207.12,239 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Benson; Walter
Assistant Examiner: Paul; Antony M
Attorney, Agent or Firm: Volpe and Koenig, P.C.
Claims
What is claimed is:
1. A method for testing a motor having a rotor and a winding,
comprising steps of: (a) providing a current to the winding to
rotate the rotor; (b) stopping the current while a rotating speed
of the rotor reaches a predetermined speed; (c) measuring a
terminal voltage of the winding while no current is within the
winding; (d) obtaining a compensated back electromotive force of
the winding by compensating the terminal voltage with a performance
of the rotor, wherein the performance includes an instantaneous
period and a rotating speed of the rotor, and the step (d) is
performed by computing the instantaneous period and the rotating
speed of the rotor and then modifying the terminal voltage to a
target rotating speed to thereby obtain the compensated back
electromotive force due to a reduction of the rotating speed; (e)
comparing the characteristic of the compensated back electromotive
force with a predetermined parameter to understand a magnetization
of the motor.
2. A method according to claim 1, wherein the motor is a
single-phase brushless direct current motor.
3. A method according to claim 1, wherein the motor is one of a
three-phase magnetic motor and a multi-phase magnetic motor.
4. A method according to claim 1, wherein the step (e) is performed
by comparing the predetermined parameter corresponding to a desired
back electromotive force with said characteristic of the
compensated back electromotive force to obtain a comparison result
and then checking whether the comparison result is within an error
scope.
5. A method according to claim 4, wherein the characteristic is a
magnitude of a respective harmonic wave of the back electromotive
force.
6. A method according to claim 4, wherein the characteristic and
the error scope are determined by at least one of an experience, a
theorem and a statistic analysis.
7. A circuit for testing a motor having a rotor and a winding,
comprising: a controlling device receiving a start signal,
providing a current to the winding to rotate the rotor, stopping a
provision of the current while a rotating speed of the rotor
reaches a predetermined value, measuring a terminal voltage of the
winding while a current within the winding reaches zero, and
obtaining a compensated back electromotive force in the winding by
compensating the terminal voltage with a performance of the rotor,
wherein the performance includes an instantaneous period and a
rotating speed of the rotor, and the controlling device computes
the instantaneous period and the rotating speed of the rotor and
then modifies the terminal voltage corresponding to a target
rotating speed to thereby obtain the compensated back electromotive
force due to a reduction of the rotating speed; and a processing
device processing a voltage signal of the winding and electrically
connected with the controlling device and the motor, wherein the
controlling device compares the characteristic of said compensated
back electromotive force with a predetermined parameter to
understand a magnetization of the motor.
8. A circuit according to claim 7, wherein the motor is a
single-phase brushless direct current motor.
9. A circuit according to claim 7, wherein the motor is one of a
three-phase magnetic motor and a multi-phase magnetic motor.
10. A circuit according to claim 7, wherein the controlling device
is electrically connected to a relay and controls a connection of
the relay so as to drive the current to the winding based on the
start signal.
11. A circuit according to claim 7, wherein the controlling device
is electrically connected to a switch and controls a connection of
the switch so as to drive the current to the winding based on the
start signal.
12. A circuit according to claim 7, wherein the controlling device
determines whether the rotating speed of the rotor reaches the
predetermined speed by a time delay.
13. A circuit according to claim 7, wherein the controlling device
determines whether the rotating speed of the rotor reaches the
predetermined speed by sampling the terminal voltage of the
winding.
14. A circuit according to claim 7, wherein the controlling device
is electrically connected to a Hall sensor and determines whether
the rotating speed of the rotor reaches the predetermined speed by
the Hall sensor.
15. A method according to claim 7, wherein the performance includes
instantaneous period and rotating speed of the rotor.
16. A method for testing a motor having a rotor and a winding,
comprising steps of: (a) providing a power to rotate the rotor to a
predetermined speed; (b) removing the power; (c) measuring a
terminal voltage of the winding while the current within the
winding is zero; (d) obtaining a back electromotive force in the
winding by compensating the terminal voltage with a performance of
the rotor, wherein the performance includes an instantaneous period
and a rotating speed of the rotor, and the step (d) is performed by
computing the instantaneous period and the rotating speed of the
rotor and then modifying the terminal voltage to a target rotating
speed to thereby obtain the compensated back electromotive force
due to a reduction of the rotating speed; (e) selecting a
characteristic of the compensated back electromotive force; and (f)
determining a magnetization of the motor by comparing the
characteristic with a predetermined parameter.
17. A method according to claim 16 wherein the motor is one
selected from a group consisting of a single-phase brushless direct
current motor, a three-phase permanent magnet motor and a
multi-phase permanent magnet motor.
Description
FIELD OF THE INVENTION
The present invention relates to a method and a circuit for testing
a motor, and more particular to the method and circuit for testing
the motor by checking and analyzing the back electromotive force of
the motor.
BACKGROUND OF THE INVENTION
The operating property of the permanent magnet motor is determined
by the magnetization property of the permanent magnet within the
motor. A magnetic analyzer with a Hall sensor is usually used to
check the qualified magnetization of the permanent magnet. Please
refer to FIG. 1, which is a drawing showing that the magnetic
analyzer is used to check the permanent magnet of the motor in the
prior art. As shown in FIG. 1, the magnetic analyzer 11 including
the probe 111 and Hall sensor 112 is used to check the permanent
magnet. After the probe 111 goes round the rotor 12, the magnetic
density of the permanent magnet's surface could be obtained.
Nevertheless, such a conventional equipment has at least the
following disadvantages. (1) It is necessary to adjust the relative
positions between the permanent magnet and probe many times during
the checking process, and it takes lots of time. (2) The probe is
relatively fragile and thus unsuitable for use on the production
line. (3) The probe has a volume. When the probe is used to check a
tiny motor, the position errors resulting from the volume of the
probe would cause an unacceptable checking error to the checking
result. (4) It is necessary to remove the core of the stator before
the checking. Therefore, the measured result is not the real
air-gap magnetic density distribution of the motor under the normal
operations. Accordingly, it is unable to perform a precise analysis
to the operation property of the motor based on the measured
result.
In addition, the quality of the permanent magnet within a permanent
magnet motor could be also determined by the back electromotive
force of the winding. An advantage of such testing method is that
the measured result could faithfully reflect the contribution of
the permanent magnet to the magnetic path and the magnetic field of
the motor during the operation of the motor. Therefore, it is
possible to precisely analyze the operation property of the
electric machinery based on the measure result. There exists no
position issue between the sensor and the permanent magnet of the
rotor. The testing result is extremely precise. Nevertheless, such
testing method has two demands: (1) the rotor must be rotating; and
(2) no driving current flows in the motor winding.
As above mentioned, a driving equipment is required for driving the
rotor of the motor to be test the voltage of the winding of the
stator i.e. the back electromotive force is obtained when the rotor
driven by driving equipment. Please refer to FIG. 2, which shows
the drawing that a driving equipment is applied for driving the
rotor of the motor to be tested in order to measure the back
electromotive force of the motor in the prior art. As shown in FIG.
2, the driving equipment includes the driving device 22
electrically connected to the driving circuit 21 to drive the rotor
23 via coupling portion 25, and then the back electromotive force
of the motor is obtained by the detector 24. Nevertheless, the
existence of the driving device 22 makes the testing system
complex. In addition, it further takes lots of time to match the
driving rotor of the driving device 22 with the rotor need to be
tested (referring to the coupling portion 25 in FIG. 2). Therefore,
the mentioned testing method is not suitable for use in the mass
production either.
As above-mentioned, in order to optimize the method for testing the
back electromotive force of the motor in the prior art and remove
the driving device 22 in FIG. 2, a new method and circuit for
testing the motor is necessary. An object of the present
application is to provide a method and circuit with the higher
preciseness, less checking time, more convenience and simpleness
based on the measuring and analysis of the back electromotive force
of the tested motor.
SUMMARY OF THE INVENTION
In accordance with an aspect of the present invention, the method
and circuit with the higher preciseness, less checking time, more
convenience and simpleness based on the measurement and analysis of
the back electromotive force of the tested motor are provided.
Firstly, the motor is started by its winding. In such case, the
winding is a driving element. Since there exists a driving current
in the winding, it is unable to measure the back electromotive
force. When the rotor is rotating at a predetermined speed, the
external power of the winding is ceased. Then, the rotor would lose
the driving torsion and rotate under the inertia. At this moment,
the winding is served as a sensor element. The back electromotive
force could be obtained by measuring the terminal voltages of the
winding.
Please refer to FIGS. 3(A) and 3(B), which show the voltage and
current waves of the winding during the testing process. FIG. 3(B)
is the magnification of the rectangular selection portion in FIG.
3(A).
As shown in FIGS. 3(A) and 3(B), it is known there are three stages
in the testing process. (S1) The motor is stared by its winding,
and at this moment, the terminal voltage of the winding is the
applied external voltage. There exists a driving current in the
winding. Nevertheless, when the rotor is rotating at a
predetermined speed higher than the necessary testing speed, the
external power to the winding is ceased. The current within the
winding would decline to zero after a period of time. (S2) In this
stage, there is no current in the winding and the winding has no
driving torsion. The rotor would keep rotating due to the inertia.
Since there is no driving current within the winding, the terminal
voltage of the winding is the back electromotive force. Therefore,
the back electromotive force could be obtained by measuring the
terminal voltage of the winding. (S3) After measuring the terminal
voltage of the winding, it is practical to quickly stop the rotor
by the winding. Such operation could save the testing time. It is
to be noted that this operation is not essential for the testing
method.
It is deserved to mention that when the motor loses the driving
torsion and rotates under the inertia, the rotating speed of the
rotor is still reducing due to the friction torsion. Such situation
is especially apparent in the motor having a load therein, such as
the cooling fan motor. For a motor having a load therein, during
the testing process, since the load always exists, the rotating
speed of the rotor would reduce apparently after the driving
torsion is removed. Furthermore, since the back electromotive force
has a direct ratio with the rotating speed of the rotator, the back
electromotive force would reduce apparently with the reduction of
the rotating speed of the rotor. Please refer to FIG. 4, which is a
diagram showing waves of the back electromotive force in FIGS. 3(A)
and 3(B) and the back electromotive force after the
compensation.
In FIG. 4, the curve 1 represents the measured back electromotive
force, and Pi (i=1, 2, 3, . . . ) represents the time of each
half-period of the back electromotive force. As shown in FIG. 4,
the back electromotive force would decline with the time, but Pi
increases with the time. Since such measuring result does not
correspond to the same rotating speed, it is unable to directly
determine the qualified magnification based thereon. Therefore, a
solution provided in the present application is to correct the
measured back electromotive force result.
If it is able to obtain the rotating speed of each moment during
the testing process, it is possible to correct all the respective
measured back electromotive forces to the corresponding back
electromotive forces for a same rotating speed. Since the back
electromotive force has a direct ratio with the rotating speed, a
corrected back electromotive force could be obtained based on the
angle of the rotor, the rotating speed and the measured back
electromotive force. For example, when the angle of the rotor is
.beta., the rotating speed is .omega., and the measured
electromotive force is e, the corrected back electromotive force
e.sub.m for a unified rotating speed .omega..sub.0 could be
obtained from the following equation.
.times..omega..omega. ##EQU00001##
Certainly, the time axis should also be corrected for the unified
rotating speed .omega..sub.0. Taking a time increment .DELTA.t at
the moment t, wherein the angle of the rotor rotating is
.DELTA..beta., then, the following equation could be obtained.
.DELTA..beta.=.omega..DELTA.t
If the rotating speed of the rotor is .omega..sub.0, the time
.DELTA.t.sub.m taken to rotate the rotor .DELTA..beta. angles would
be obtained in following equation.
.DELTA..times..times..omega..omega..times..DELTA..times..times.
##EQU00002##
If the sum of rotating angle of the motor from the initial time
t.sub.0 to time t is B, then the time t.sub.m for the motor to
rotate from t.sub.0 to have a sum rotating angle B under the
rotating speed .omega..sub.0 could be obtained from the following
equation.
.intg..times..omega..omega..times.d ##EQU00003##
The back electromotive force wave II shown in FIG. 4 is the wave
after the speed correction. As shown in FIG. 4, it is known the
corrected back electromotive forces have corresponded to the same
rotating speed.
The rotating speed of the motor reduces regularly. In the present
application, the regulation of the speed-reduction of the motor is
used to obtain the rotating speed of the rotor at a specific time
by analyzing the corresponding measured back electromotive force.
Taking the wave I shown in FIG. 4 as an example, the respective
instantaneous rotating speed .omega..sub.i of the rotor at the
individual middle point t.sub.i (i=1, 2, . . . ) of each
half-period could be similarly obtained from the following
equation.
.omega..pi. ##EQU00004## wherein the corresponding instantaneous
period is 2P.sub.i.
The change of the rotating speed of the motor is determined by the
following equation, wherein the rotating inertia of the rotor is J
and the load torsion is T.sub.L.
.times.d.omega.d ##EQU00005##
Since the load of the motor is various, the regulation of the
speed-reduction of the motor is various. It could be proved that,
where there is no load on the motor, a relationship between the
instantaneous period 2P.sub.i and the time t has a linear increase,
as show in FIG. 5. According to such a relationship, when some
instantaneous periods 2P.sub.is for various time t.sub.is are
measured, it is possible to predict the other instantaneous period
2P and then the corresponding instantaneous rotating speed .omega.
could be found via the following equation.
.omega..pi. ##EQU00006##
With regard to other load of the motor, the relationship between
the instantaneous period 2P.sub.i and the time t could be show as
FIG. 6. When the load is accurately known, it is also possible to
obtain the accurate relationship between the instantaneous period
2P.sub.i and the time t. Nevertheless, in practice, it is difficult
to know the accurate load sometimes. In some cases, the load would
be various with the changing rotating speed. In such cases, it is
difficult to obtain a clear relationship between the instantaneous
period and the time. As mentioned above, it would be more efficient
to use the interpolation to the known relationship as shown in FIG.
6 so as to obtain the instantaneous period and the corresponding
rotating speed for a specific time within the relationship.
For the motor having the rotor with great inertia and small load,
since the measured rotating speed reduction is no apparent, it is
practical to omit the correcting step to the measured result.
It is possible to determine whether the magnetization of the motor
is qualified after comparing the corrected back electromotive force
with the expected value of the back electromotive force. A
characteristic of the corrected back electromotive force might be
compared with a characteristic of the expected back electromotive
force. Certainly, the corrected back electromotive force has many
characteristics, so that it is possible to perform the comparisons
for more than one characteristics. As those well-known to one
skilled in the art, the reliability of the comparison results and
the amount of the analysis data both would increase with the amount
of the compared characteristics. If the selected characteristics
are all within the relevant error scopes, as showing in the
following equation (wherein EG.sub.i, EG.sub.bi and EG.sub.ti are
the measured value, the expected value and the allowable error of
the i.sup.th characteristic), it is practical to determine that the
measured back electromotive force is qualified, i.e. the permanent
magnetization of the measured rotor is qualified.
|EG.sub.i-EG.sub.bi|<EG.sub.ti i=1,2, . . . n
Please refer to FIG. 7, which is a diagram showing the comparison
between the wave of the measured and corrected back electromotive
force and the wave of the expected back electromotive force. In
FIG. 7, c2 is the wave of the measured and corrected back
electromotive force, c1 is the wave of the expected back
electromotive force, and .DELTA.E.sub.max is the maximum error of
the selected characteristic. Please refer to FIG. 8, which is a
diagram showing the comparisons of the harmonic wave weight
amplitudes of the measured and corrected back electromotive force
and the expected back electromotive force in FIG. 7. In FIG. 8,
A.sub.i, A.sub.bi and .DELTA.A.sub.i (i=1, 2, . . . ) are the
measured value, the expected value and the error of the respective
harmonic wave weight amplitude, and the respective selected
characteristic represents the respective A.sub.i. Finally, the
allowable tolerances for the error scopes could be determined by
the relevant operating experiences, theorems or the analysis of the
statistics of measurements of the qualified rotors. The allowable
error is used for the consideration of the dispersity between the
measurement and the magnetization. Such dispersity could be
obtained by the statistics of the measurements. A common method
includes the following steps of: 1. providing some qualified
rotors, 2. measuring the back electromotive forces of the qualified
rotors, 3. statistically analyzing the measurements of the back
electromotive forces, 4. gathering the statistics of the respective
expected value EG.sub.bi and variance .delta..sub.i of the selected
characteristics. Then the respective allowable error EG.sub.ti
could be defined as k.delta..sub.i, wherein k is a factor. The
testing precision of the back electromotive force is controlled by
the selection of the factor k. The above contents and advantages of
the present invention will become more readily apparent to those
ordinarily skilled in the art after reviewing the following
detailed descriptions and accompanying drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a drawing showing that the magnetic analyzer is used to
check the permanent magnet of the motor in the prior art;
FIG. 2 shows the drawing that a driving equipment for driving the
rotor of the motor to be checked is applied in order to measure the
back electromotive force of the motor in the prior art;
FIGS. 3(A) and 3(B) show the voltage and current waves of the
winding during the testing process;
FIG. 4 is a diagram showing waves of the back electromotive force
in FIGS. 3(A) and 3(B) and the back electromotive force after the
compensation;
FIG. 5 shows the relationship between the instantaneous period
2P.sub.i and the time t where there is no load on the motor;
FIG. 6 shows the relationship between the instantaneous period
2P.sub.i and the time t when a specific load is applied;
FIG. 7 is a diagram showing the comparison between the wave of the
measured and corrected back electromotive force and the wave of the
expected back electromotive force;
FIG. 8 is a diagram showing the comparisons of the harmonic wave
weight amplitudes of the measured and corrected back electromotive
force and the expected back electromotive force in FIG. 7;
FIG. 9 is a circuit diagram showing the use of the provided method
to the single-phase brushless direct current motor according to a
preferred embodiment of the present application;
FIG. 10 is a diagram showing the terminal voltages of the winding
and the relevant filter wave during the starting process;
FIG. 11 is the diagram showing the wave of the terminal voltages of
winding during the starting process of the motor;
FIG. 12 is a circuit diagram showing the use of the provided method
to the three-phase permanent magnetic motor according to a
preferred embodiment of the present application;
FIG. 13, which is a circuit diagram showing the use of the provided
method to the three-phase permanent magnetic motor according to
another preferred embodiment of the present application;
FIG. 14 is a circuit diagram showing the use of the provided method
to the single-phase brushless direct current motor according to a
preferred embodiment of the present application; and
FIG. 15 is the flow chart for the testing method according to a
preferred embodiment of the present application.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention will now be described more specifically with
reference to the following embodiments. It is to be noted that the
following descriptions of preferred embodiments of this invention
are presented herein for purpose of illustration and description
only; it is not intended to be exhaustive or to be limited to the
precise form disclosed.
Please refer to FIG. 9, which is a circuit diagram showing the use
of the provided method to the single-phase brushless direct current
motor according to a preferred embodiment of the present
application. The main testing circuit includes the digital
controlling device 31 and the signal processing circuit 32. In
addition, the start key 37, the relay 36, the power source Vcc, the
motor 35 having the driving circuit 33 and the motor winding 34,
and other components (such as the resistors R1 and R2) are also
shown in FIG. 9.
As shown in FIG. 9, the digital controlling device 31 is used to
control, sample the back electromotive force and process the
signal. The signal processing circuit 32 is used to modify the
signal of the back electromotive force. The digital controlling
device 31 sends a control signal TK to turn-on or turn-off the
relay 36. Before performing the testing method of the present
application, the start key 37 is in a normal condition, and the
start signal ST is in a relatively lower potential level.
When the start key 37 is pressed for performing the method of the
present application, the start signal ST would have a relatively
higher potential level. After receiving the start signal ST with
higher potential level, the digital controlling device 31 sends
turn-on signal TK to close the contact of the relay 36 so as to
provide the current to the driving circuit 33 to drive the rotor to
be tested.
After the digital controller 31 operates for a proper period, the
contact of the relay 35 is turn-off and then the driving circuit 33
would not supply power to the motor. The period is determined by a
timer to ensure that the rotor of the motor has reached a specific
rotating speed for sampling the back electromotive force signal
latter. At this moment, the winding 34 would have no external
current and then be in the freewheeling status.
The digital controlling device 31 delays for a second proper period
which is determined by the timer to ensure the current within the
winding 34 has reduced to zero, and then the digital controlling
device 31 starts the analog to digital (A/D) transform for sampling
the adjusted back electromotive force signals. After obtaining
enough sampling data, the digital controlling device 31 stops the
analog to digital (A/D) transform and then modify the sampled BEMF
corresponding to the decreasing rotating speed. Comparing the
modified BEMF with the predetermined expected back electromotive
force and amount of allowable error, the digital controlling device
31 determines whether the back electromotive force of the tested
rotor is qualified, i.e. the digital controller 31 determines
whether the permanent magnetization of the motor is qualified.
As above, the time delay technology of the timer is used to ensure
the rotor has been accelerated to a specific speed. Nevertheless,
during the starting process, since the terminal voltages of the
winding 34 reflect the rotating speed of the motor, it is practical
to sample the terminal voltages of the winding 34 via the digital
controlling device 31 to test whether the rotor of the motor has
reached the desired rotating speed. Please refer to FIG. 10, which
is a diagram showing the terminal voltages of the winding and the
relevant filter wave during the starting process. In FIG. 10, Vab
is the sampled voltage signal of the winding. Since the general
motor controller applies a pulse width modulation (PWM) soft-start
technology, the sampled voltage signals are also the pulse signals.
The digital controlling device 31 performs a digital filtering to
the PWM wave and the filtered wave is Vabm. Based on the over-zero
point of the Vabm, it is possible to obtain the period 2T of the
motor, and then it is possible to determine whether the rotating
speed of the motor has reached the desired speed accordingly. In
addition, it is usual to exist a phase delay between the filtered
voltage signal Vabm and the original sampled signal Vab.
Nevertheless, the time for such a phase delay is usually short and
the system is not so critical to the real-time property, such delay
could be omitted.
Since the back electromotive force has an apparent regulation, it
is possible to determine whether the current within the winding 34
is zero by measuring the terminal voltages of the winding 34 after
turning off the relay 36 via the digital controlling device 31.
Please refer to FIG. 11, which is the diagram showing the wave of
the terminal voltages of winding during the starting process of the
motor. In FIG. 11, the digital controlling device 31 turns off the
relay 36 to turn off the power Vcc and the winding 34 at the moment
t.sub.b. Then, the winding 34 operates under the freewheeling
status. The time intervals between the over-zero points of the
terminal voltages of winding 34 are recorded from the moment
t.sub.b. When the following relationships are achieved, wherein s
is a positive integral, it is able to determine the current within
the winding 34 is zero. It is to be noted that when the s
increases, the requirement becomes stricter, but, in general, s is
1 or 2. T.sub.i.apprxeq.T.sub.i-1.apprxeq.T.sub.i-2 . . .
.apprxeq.T.sub.i-s and T.sub.i.gtoreq.T.sub.i-1.gtoreq.T.sub.i-2 .
. . .gtoreq.T.sub.i-s
Please refer to FIG. 12, which is a circuit diagram showing the use
of the provided method to the three-phase permanent magnetic motor
according to a preferred embodiment of the present application. As
shown in FIG. 12, the motor 35 includes the three-phase winding 34
and the three-phase driving circuit 33, and the other components
are the same as those in FIG. 9. In the three-phase motor 35, the
three phase windings U, V and W are connected as a star, the signal
processing circuit 32 is connected electrically to the winding U
and the neutral point N. Therefore, the back electromotive force
received by the digital controlling device 31 is that of the
winding U. The other control methods are the same as those for FIG.
9 and are omitted herein.
Please refer to FIG. 13, which is a circuit diagram showing the use
of the provided method to the three-phase permanent magnetic motor
according to another preferred embodiment of the present
application. The difference between FIG. 12 and FIG. 13 is that the
signal processing circuit 32 is connected electrically to the
windings U and V in FIG. 13. Therefore, what received by the
digital controlling device 31 is the linear back electromotive
force of the windings. The other control methods are the same as
those for FIG. 9 and are omitted herein.
Please refer to FIG. 14, which is a circuit diagram showing the use
of the provided method to the single-phase brushless direct current
motor according to a preferred embodiment of the present
application. The difference between FIG. 14 and the aforesaid
embodiments is that plural switches (such as transistors) G1-G4 are
used to replace the relay 36 and the driving circuit 33, and a Hall
sensor 38 is provided to obtain the location information of the
motor rotor in FIG. 14.
During the operation, the digital controlling device 31 sends
control signals T1, T2, T3 and T4 to the switches G1, G2, G3 and G4
based on the location information transmitted from Hall sensor 38
so as to control the operating status of the motor. When the start
key 37 is pressed, the digital controlling device 31 would send the
corresponding control signals to the switches based on the location
of the rotor and then apply the driving voltage to the winding 34.
Then the rotating speed of the rotor would increase, and the
digital controlling device 31 determines whether the rotating speed
of the rotor has achieved a desired value by the location signal
from the Hall sensor 38. When the rotating speed of the rotor has
achieved the desired value, the digital controlling device 31 turns
off the switches G1-G4. Then, the digital controlling device 31
samples the information about the back electromotive force of the
winding 34, performs the follow-up compensation, analysis and
comparisons of the sampled back electromotive force.
The mentioned embodiments are used for describing the present
application but not limited to the circuit structures of the
present application. In practice, various applications relating to
the controlling device 31 and the signal processing circuit 32 of
the present application are still within the spirit and scope of
the appended claims. In order to further realize the present
application, please refer to FIG. 15, which is the flow chart for
the testing method according to a preferred embodiment of the
present application.
In FIG. 15, S1 represents the step of pressing the start key, S2
represents the step of providing the current to the winding to
rotate the rotor from the power source, S3 represents the step of
waiting until the rotating speed of the rotor reaches a threshold
value, S4 represents the step of stopping the provision of the
current to the winding after the rotating speed of the rotator
reaches the threshold value, S5 represents the step of waiting
until the current within the winding reduced to zero, S6 represents
the step of measuring the terminal voltages of the winding while
the rotor freewheeling and then a back electromotive force is
obtained, S7 represents the step of obtaining a compensated back
electromotive force by at least a performance value of the rotor
during the measuring of the terminal voltages of the rotor, S8
represents the step of analyzing the compensated back electromotive
force and selecting at least a characteristic of the compensated
back electromotive force, S9 represents the step of comparing the
at least a characteristic of the compensated back electromotive
force with the corresponding characteristic of the expected back
electromotive force to obtain a result, and S10 represents the step
of outputting the result to determine whether the magnetization of
the motor is qualified, and then the mentioned steps are performed
to the next rotor.
While the invention has been described in terms of what is
presently considered to be the most practical and preferred
embodiment, it is to be understood that the invention needs not be
limited to the disclosed embodiments. On the contrary, it is
intended to cover various modifications and similar arrangements
included within the spirit and scope of the appended claims which
are to be accorded with the broadest interpretation so as to
encompass all such modifications and similar structures.
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